Amorphization of Ni₆₀Nb₂₀Zr₂₀ by mechanical alloying

Elemental Ni, Nb and Zr powder mixtures with composition Ni60Nb20Zr20 were mechanically alloyed in a ball mill. The evolution of structure of the powders was investigated with a combination of X-ray diffractometry and differential scanning calorimetry and was compared with corresponding melt spun samples. Mechanical alloying of Ni60Nb20Zr20 alloy involves two consecutive amorphization reactions. Mechanical alloying first leads to the amorphization reaction between Ni and Zr layers with a strong thermodynamic driving force as well as fast kinetics for Ni-Zr amorphization compared with Ni-Nb amorphization. On further milling the kinetic requirements for a Ni-Nb amorphization reaction is fulfilled and consequently a Ni-Nb amorphous phase forms. The resulting two amorphous phases homogenize at longer milling times.